The invention relates to an agricultural sowing machine with a press wheel for the precise application of seeds.
A single grain sowing machine is known from U.S. Pat. No. 4,141,302 A, in which seed is deposited at defined distances in a furrow opened by a double disc coulter. In order to prevent a rolling about of the seed within the furrows, the seed is pressed with a press wheel into the bottom of the furrow. A similar device is presented in the German application DE 10 2013 111 355, however, with two double disc coulters placed at an angle to each other with intermediate depth guide rollers, wherein press wheels are also assigned to the respective double disc coulters, which immediately after the seed discharge press the seed grains into the bottom of the furrow. In order to prevent a caking or blocking of the press wheels in the furrow in difficult, sticky soil conditions, the European patent application EP 404 241 A1 proposes a press wheel driven at approximately the travelling speed of the sowing machine, which prevents a displacement of the seed grains within the furrows. A further form of a press wheel is described in the European patent EP 1461 988 B1, wherein an elastic, rectangular hollow tire fills the U-shaped furrow cross section of a coulter shoe behind a double disc coulter and projects beyond its lower edge and the seed grains pressed. Via a claimed length-width ratio of at least 2:1, preferably 3:1, a self-cleaning flexing effect of the hollow tire is to be achieved. A rigid rim body with a clamping groove for the tire is thereby guided nearly up to the hollow body of the tire. In particular, when the sowing machine is inserted into the soil, in the case of a non-rectangular furrow execution and in the case of cornering this leads to unwanted deformation of the hollow tire, whereby the latter cannot be guided cleanly over the deposited seed grains or even emerge from the furrow cross section. The applicant itself speaks of a flabby execution. In the later publication DE 10 2012 108 006 A1 of the same applicant the roller is supposed to be folded up or removed in the case of wet and sticky soil conditions.